I’ve got a lot of ice in my gutters around my roof, and it’s contributing to the formation of ice dams. I’d like to pour salt into them and melt it off. The gutters are pure aluminum. Can the salt damage them? I see many other houses with horribly corroted gutters, but they may be steel.
I’ve always been under the impression aluminum doesn’t rust, but I want to be sure.
Aluminum rusts very readily, but the oxidation is extremely stable so only a tiny thin layer on the surface rusts. So Al still looks nice and shiny thru that layer. It usually takes something like contact with a different metal to get significant corrosion (due to electrochemical processes). So only use Al nails with Al surfaces, etc.
A much better solution to ice dams is to add insulation to your attic. It’s a win-win. Your roof lasts longer and your heating bill goes down. It pays for itself.
Aluminium doesn’t rust the same way as iron or steel does. However, in terms of oxidation, aluminium oxidises far more readily than iron or steel. Like iron, aluminium forms Al[sub]2[/sub]O[sub]3[/sub] (aluminium oxide) with oxygen, and Al(OH)[sub]3[/sub] (aluminium hydroxide) with water.
However, aluminium hydroxide and oxide do not flake off as easily as those of iron. They are also insoluble in water, especially cold water. Hence they form a protective layer around the pure aluminium inside, preventing further oxidation. This is why aluminium is used as a coating in electrolysis - the properties of aluminium oxide and hydroxide will sufficiently protect the metal within.
Salt can 'pit" aluminum. Also, anywhere this water runs off will damage the soil. Salt and grass = dead grass.